1. Technical Field
The present disclosure relates to an image sensor and to a method of manufacturing the same, and more particularly, to an image sensor which may simultaneously control sensitivity and color mixing characteristics and to a method of manufacturing the same.
2. Description of the Related Art
Image devices may be defined as photoelectric conversion elements that monitor light to convert it into an electrical signal. FIG. 1 schematically illustrates an image sensor according to a conventional technique.
Referring to FIG. 1, a conventional image sensor 10 includes a plurality of pixels (not shown) arranged as a matrix on a P-type epitaxial layer 13. Each pixel includes a photodiode PD and transistors (not shown). The photodiode PD monitors external light and generates optical charges. The generated optical charges are then gathered in the photodiode PD. Next, the transistors provide an electrical signal according to the generated optical charges.
However, the depth of a region where the photodiode PD may gather electrons is restricted. For example, electrons generated in a region deeper than the gatherable region may cause a crosstalk phenomenon to occur. The crosstalk phenomenon may occur when optical charges generated in a semiconductor layer of a semiconductor substrate do not migrate to a photodiode of a corresponding pixel but instead migrate to a photodiode of a neighboring pixel. The above-mentioned crosstalk may in turn degrade the color reproducibility of the image sensor.
The crosstalk phenomenon is now even more significant as a result of the current tendency toward increasing the integration of the image sensors. For example, as a result of the increasing integration of the image sensors, the distance between pixels may become shortened, and the dimensions of the photodiode of these image sensors may be decreased, which in turn may increase the probability that, the optical charges generated in the semiconductor layer of the semiconductor substrate may migrate to a photodiode of a neighboring pixel.
Thus, to overcome the above-mentioned crosstalk phenomenon, a conventional image sensor was developed and will be explained in further detail below. The conventional image sensor 10 includes an Ndrain layer 12 under the pixel array (not shown) to externally drain electrons having a color mixing component. Moreover, to externally drain the color mixing component, a power source voltage VDD is supplied to the Ndrain layer 12 of the image sensor 10.
In addition, to supply the power source voltage VDD to the Ndrain layer 12, the image sensor 10 has a power source connection element 14 that electrically connects the Ndrain layer 12 to the power source voltage VDD.
FIG. 2 is a graph representing a potential formed along a dotted line X-X′ of FIG. 1.
Referring to FIGS. 1 and 2, by supplying the power source voltage VDD to the Ndrain layer 12, an energy barrier such as a region b is formed to solve the difficulty that results from the crosstalk phenomenon caused by migration of an optical charge (e−) to another pixel.
However, because with the conventional image sensor, the voltage is overly applied to the drain layer 12 to drain the color mixing component that causes the crosstalk, a signal component may also be drained. Consequently, the sensitivity characteristics of the image sensor may also be adversely degraded. In other words, the sensitivity characteristics of the conventional image sensor may have to be sacrificed in order to prevent the color mixing phenomenon caused by the crosstalk.